David Koren

Bio: David Koren is an academic researcher from University of Ljubljana. The author has contributed to research in topics: Base isolation & Thermal insulation. The author has an hindex of 9, co-authored 22 publications receiving 343 citations.

Resilience assessment of complex urban systems to natural disasters: A new literature review

Abstract: In parallel with the observed greater frequency of natural disasters worldwide, there has been an ever-increasing interest in urban resilience and its assessment. Experience obtained in recent extreme events (in particular, earthquakes and floods) has revealed that both the level of preparedness and the response of affected cities were insufficiently high, whereas the recovery process was long and expensive. For this reason improved pre-disaster mitigation actions, as well as smart and strategic urban planning in threatened areas (e.g. in earthquake-prone regions), is essential. For this purpose, a comprehensive review of the existing literature has been performed in relation to the holistic assessment of urban system resilience to natural disasters, with an emphasis on the effect of earthquakes. The main goal of the review was to try to determine how to best assess the resilience of urban systems as a whole, taking into account all of their components, i.e. both the physical components (i.e. of buildings, infrastructure, and open spaces) and the social components (i.e. of the community), as well as the dynamic interactions between them. Besides considering the commonly measured indicators (e.g. determination of the scope of actual structural damage caused by an earthquake), the paper tries to extend the discussion to some indicators which are not so commonly taken into account, by applying a quantitative resilience assessment approach. Based on the results of the described new literature review, a preliminary concept which could be used to assess the seismic resilience of complex urban systems, taking into account all urban components which have been identified as having an important impact on the latter, is presented. This concept consists of three different parts: (i) a probabilistic fragility analysis for each individual physical element (i.e. a building or an infrastructure element), (ii) a composite index methodology for the measurement of community disaster resilience, and (iii) a complex network approach (graph theory) for the assessment of the resilience of urban systems as a whole. Since, in the existing literature, there is a lack of consideration of urban open space, which can have a significant role in the recovery process, it is suggested that, in future research of seismic resilience assessment, such open space should be taken into account, and that an in-depth study of possible recovery strategies be performed.

Simplified inelastic seismic analysis of base‐isolated structures using the N2 method

Abstract: In the paper a simplified nonlinear method has been applied to the analysis of base-isolated structures. In the first part, a three-linear idealization of the capacity curve is proposed. The initial stiffness is defined based on the first yielding point in the superstructure, whereas the secondary slope depends on the failure mechanism of the superstructure. A consequence is a much more pronounced secondary slope, which does not correspond to the presumptions used in the originally proposed N2 method. A parametric nonlinear dynamic study of single degree of freedom systems with different hardening slopes and damping has been performed for an ensemble of seven EC8 spectrum-compatible artificial accelerograms. It was concluded that, in the long-period range, the equal displacement rule could be assumed also for the proposed systems with non-zero post-yield stiffness. In the second part, the proposed idealization was used for the analysis of isolated RC frame buildings that were isolated with different (lead) rubber-bearing isolation systems. The stiffness of the isolators was selected for three different protection levels and for three different ground motion intensities, which have resulted in elastic as well as moderately and fully damaged superstructure performance levels. Three different lateral load distributions were investigated. It was observed that a triangular distribution, with an additional force at the base, works best in the majority of practical cases. It was concluded that the N2 method can, in general, provide a reasonably accurate prediction of the actual top displacement, as well as of the expected damage to the superstructure. Copyright © 2009 John Wiley & Sons, Ltd.

The potential of open space for enhancing urban seismic resilience : a literature review

Abstract: For a city to perform successfully, and its citizens to feel safe and comfortable, the health of basic urban components and the overall resilience of the urban system is crucial. As the importance of the resilient urban system has been recognized in the scientific literature, many studies have been done on this topic. Therefore, to find out the gaps in the existing literature and the opportunities for further research, a new systematic literature review has been performed in three stages. Different bibliographic techniques (co-occurrence and co-citation analysis) have been applied and, in the final stage of the analysis, an in-depth study of the content of the selected papers addressing open space in relation to urban seismic resilience has been carried out. The obtained results and trends have shown a lack of research on the potential of open space for enhancing urban seismic resilience, as well as a challenge for its quantitative assessment. The ability of the affected resilient system is to achieve at least a pre-disaster performance level in an acceptable time, which can be gained, among others, by using the restorative potential of open space. Based on the synthesis of these findings the authors’ draft model of an urban system integrating the potential of open space is presented in terms of a complex network theory.

Seismic Design Of Reinforced Concrete And Masonry Buildings

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The Emilia Earthquake: Seismic Performance of Precast Reinforced Concrete Buildings

Abstract: On 20 and 29 May 2012, two earthquakes of MW5.9 and MW5.8 occurred in the Emilia region of northern Italy, one of the most developed industrial centers in the country. A complete photographic report collected in the epicentral zone shows the seismic vulnerability of precast structures, the damage to which is mainly caused by connection systems. Indeed, the main recorded damage is either the loss of support of structural horizontal elements, due to the failure of friction beam-to-column and roof-to-beam connections, or the collapse of the cladding panels, due to the failure of the panel-to-structure connections. The damage can be explained by the intensity of the recorded seismic event and by the exclusion of the epicentral region from the seismic areas recognized by the Italian building code up to 2003. Simple considerations related to the recorded acceleration spectra allow motivating the extensive damage due to the loss of support.

Resilience assessment of complex urban systems to natural disasters: A new literature review

Abstract: In parallel with the observed greater frequency of natural disasters worldwide, there has been an ever-increasing interest in urban resilience and its assessment. Experience obtained in recent extreme events (in particular, earthquakes and floods) has revealed that both the level of preparedness and the response of affected cities were insufficiently high, whereas the recovery process was long and expensive. For this reason improved pre-disaster mitigation actions, as well as smart and strategic urban planning in threatened areas (e.g. in earthquake-prone regions), is essential. For this purpose, a comprehensive review of the existing literature has been performed in relation to the holistic assessment of urban system resilience to natural disasters, with an emphasis on the effect of earthquakes. The main goal of the review was to try to determine how to best assess the resilience of urban systems as a whole, taking into account all of their components, i.e. both the physical components (i.e. of buildings, infrastructure, and open spaces) and the social components (i.e. of the community), as well as the dynamic interactions between them. Besides considering the commonly measured indicators (e.g. determination of the scope of actual structural damage caused by an earthquake), the paper tries to extend the discussion to some indicators which are not so commonly taken into account, by applying a quantitative resilience assessment approach. Based on the results of the described new literature review, a preliminary concept which could be used to assess the seismic resilience of complex urban systems, taking into account all urban components which have been identified as having an important impact on the latter, is presented. This concept consists of three different parts: (i) a probabilistic fragility analysis for each individual physical element (i.e. a building or an infrastructure element), (ii) a composite index methodology for the measurement of community disaster resilience, and (iii) a complex network approach (graph theory) for the assessment of the resilience of urban systems as a whole. Since, in the existing literature, there is a lack of consideration of urban open space, which can have a significant role in the recovery process, it is suggested that, in future research of seismic resilience assessment, such open space should be taken into account, and that an in-depth study of possible recovery strategies be performed.